PortentsThe World Without UsEach day birds must run a deadly gantlet of cell towers, cats, and other modern perils. But would they thrive if humans suddenly vanished and nature healed itself? A scenario as compelling as this confronts us with our role in wiping out some species and taking responsibility for saving others. By Alan WeismanIllustrations by John James Audubon

A generation ago humans eluded nuclear annihilation; with luck we’ll continue to dodge that and other mass terrors. Our latest crisis, however, springs from something far more subtle and insidious than atomic bombs. Has our very daily existence, we wonder, inadvertently poisoned or parboiled the planet?

We’ve also used and abused water and soil so that there’s a lot less of each, and trampled thousands of species that probably aren’t coming back. Our world, some respected voices warn, could one day degenerate into something resembling a vacant lot, where crows and rats scuttle among weeds, preying on each other. If it comes to that, at what point would things have gone so far that, for all our vaunted superior intelligence, we’re not among the hardy survivors?

The truth is, we don’t know. We may be undermined by our survival instincts, honed over eons to help us deny, defy, or ignore catastrophic portents lest they paralyze us with fright.

If those instincts dupe us into waiting until it’s too late, that’s bad. If they fortify our resistance in the face of mounting omens, that’s good. More than once, crazy, stubborn hope has inspired creative strokes that snatched people from ruin. So let us try a creative experiment: Suppose that the worst has happened. Human extinction is a fait accompli. Not by nuclear calamity, asteroid collision, or anything ruinous enough to also wipe out most everything else, leaving whatever remained in some radically altered, reduced state. Nor by some grim eco-scenario in which we agonizingly fade, dragging many more species with us in the process.

Instead, picture a world from which we all suddenly vanished. Tomorrow.

Unlikely, perhaps, but for the sake of argument, not impossible. Say a Homo sapiens-specific virus—natural or diabolically nano-engineered—picks us off but leaves everything else intact. Or some misanthropic evil wizard somehow targets that unique 4 percent of DNA that makes us human beings and not chimpanzees, or perfects a way to sterilize our sperm.

Look around you, at today’s world. Your house, your city. The surrounding land, the pavement underneath, and the soil hidden below that. Leave it all in place but extract the human beings. Wipe us out, and see what’s left. How would the rest of nature respond if it were suddenly relieved of the relentless pressures we heap on it and our fellow organisms? How soon would, or could, the climate return to where it was before we fired up all our engines? And what would become of the species that shared the planet with us?

In a world without humans, what will be left for birds? What will be left of birds? Of the more than 10,000 species that we know have coexisted with us, ranging from hummingbirds that weigh less than a penny to 600-pound wingless moas, about 130 have disappeared. That is barely more than one percent, almost an encouraging figure if some of these losses hadn’t been so sensational. Moas stood 10 feet tall and weighed twice as much as an African ostrich. They were extinguished within two centuries by Polynesians who sometime around A.D. 1300 colonized the last major planetary landmass that humans discovered, New Zealand. By the time Europeans appeared some 350 years later, piles of big bird bones and Maori legends were all that remained.

Other massacred, flightless birds include the dodo of the Indian Ocean’s Mauritius Island, famously clubbed and cooked to death within a hundred years by Portuguese sailors and Dutch settlers it never learned to fear.

The most stunning avicide of all, just a century ago, is still hard to fathom in its enormity. By anyone’s estimate, the North American passenger pigeon was the most abundant bird on earth. Its flocks, 300 miles long and numbering in the billions, spanned horizons fore and aft, actually darkening the sky. Hours could go by, and it was as though the birds hadn’t passed at all, because they kept coming. Larger, far more striking than the ignoble pigeons that soil our sidewalks and statuary, these were dusky blue, rose-breasted, and apparently delicious. Long before we had poultry factories to mass-produce chicken breasts by the billion, nature did much the same.

They ate unimaginable quantities of acorns, beechnuts, and berries. One of the ways we slew them was by cutting their food supply, as we sheared forests from the eastern United States to plant our own food. The other was with shotguns, spraying lead pellets that could down dozens with a single blast. After 1850, with most of the heartland forest gone to farms, hunting passenger pigeons was even easier, as millions of them roosted together in the remaining trees. Boxcars stuffed with them arrived daily in New York and Boston. When it finally became apparent that their unthinkable numbers were actually dropping, a kind of madness drove hunters to slaughter them even faster while they were still there to kill. By 1900 it was over. A miserable few remained caged in a Cincinnati zoo, and by the time zookeepers realized what they had, nothing could be done. The last one died before their eyes in 1914.

In succeeding years, the parable of the passenger pigeon was retold often, but its moral could only be heeded in part. A conservation movement founded by hunters themselves, Ducks Unlimited, has bought millions of acres of marshland to ensure that no game species they value will be without places to land and breed. However, in a century in which humans proved more inventive than during the rest of Homo sapiens’ history combined, protecting life on the wing became more complicated than simply making game-bird hunting sustainable.

Red-eyed vireo
Threat: Transmission towers Like most songbirds, red-eyed vireos take red-eye flights, migrating at night. The skies that once provided safe passage are now interrupted by tall transmission towers, and the death toll for birds colliding with these towers now runs to the hundreds of millions.

Unknown to most people, except for a small circle of scientists who have been connecting the dots for decades, our TVs, cell phones, and even our cars have wreaked unprecedented avian slaughter. Consider, for example, the Lapland longspur. It isn’t commonly known to North Americans, because its behavior isn’t quite what we expect from migratory birds. Its summer and breeding grounds are in the high Arctic, so just as more familiar songbirds head to points south, Lapland longspurs arrive to spend the winter in the great plains of Canada and the United States.

They’re pretty little black-faced, finch-sized birds with white half-masks and russet patches on their wings and nape, but we mostly see them at a distance: hundreds of indistinct, small birds swirling in the winter prairie wind, picking over fields. On the morning of January 22, 1998, however, they were easy to see in Syracuse, Kansas, because nearly 10,000 were lying frozen on the ground. During a storm the previous evening, a flock crashed into a cluster of radio transmission towers. In the fog and blowing snow, the only things visible were red, blinking lights, and the longspurs apparently headed for them.

Neither the circumstances nor the numbers of their deaths were particularly unusual, although the toll for a single evening was possibly high. Reports of dead birds heaped around the bases of TV antennae started getting ornithologists’ attention in the 1950s. By the 1980s estimates of 2,500 deaths per tower, per year, were appearing.

In 2007 some 93,000 towers were registered with the Federal Communication Commission, although this number is thought to be underreported by as much as 35 percent. Many are higher than 199 feet, which means that they are required to have warning lights for aircraft. If calculations by scientists are correct, that means that some 3 million to 4 million birds collide fatally with towers each year in the United States alone, although the number could be as high as 30 million to 50 million. Still, these numbers are based on scant data and on guesses, because scavengers get to most feathered victims before they’re found.

From ornithology labs east and west of the Mississippi, graduate students were sent on grisly night missions to transmitter towers to recover the carcasses of red-eyed vireos, Tennessee warblers, Connecticut warblers, orange-crowned warblers, black-and-white warblers, ovenbirds, wood thrushes, yellow-billed cuckoos . . . the lists became an increasingly thorough compendium of North American birds, including rare species like the red-cockaded woodpecker. Especially prominent were birds that migrate, and especially those that travel at night.

One is the bobolink, a black-breasted, buff-backed plains songbird that winters in Argentina. By studying its eyes and brains, bird physiologist Robert Beason has detected evolutionary traits that unfortunately turned lethal in the age of electronic communications. Bobolinks and other migrants carry built-in compasses—particles of magnetite in their heads, with which they orient to the earth’s magnetic field. The mechanism to switch them on involves their optics. The short end of the spectrum—purples, blues, and greens—apparently triggers their navigational cues. If only longer red waves are present, they grow disoriented.

Beason’s observations also suggest that migrating birds evolved to fly toward light in foul weather. Until electricity, this meant the moon, which would put them out of harmful weather’s way. Thus, a pulsating tower bathed in a red glow whenever fog or blizzard blots out everything else is as seductive and deadly to them as wailing Sirens to Greek sailors. With their homing magnets befuddled by a transmitter’s electromagnetic fields, they end up circling its towers, whose guy wires become the blades of a giant bird blender.

In a world without humans, the red lights will blink off as broadcasts cease, a billion daily cellular conversations will disconnect, and several billion more birds will be alive a year later. But as long as we’re still here, transmission towers are only the beginning of the unintended carnage human civilization perpetrates on feathered creatures we don’t even eat.

Harris’s hawk
Threat: Power lines Power lines may serve as handy perches for birds, but they also electrocute many that brush two wires at once or come in contact with uninsulated transformers. In open country in the Southwest, the Harris’s hawk is one frequent victim.

A different kind of tower—frameworks of steel lattice averaging 150 feet tall—marches the length and breadth and diagonally across every continent save Antarctica. Suspended between these structures are aluminum-clad high-tension cables bearing millions of sizzling volts from power plants to our energy grids. Some are three inches thick; to save weight and cost, all are uninsulated.

There’s enough wire in North America’s grid alone to reach the moon and back, and nearly back again. With the clearing of forests, birds learned to perch on telephone and power lines. As long as they don’t complete a circuit with another wire or with the ground, they don’t electrocute themselves. Unfortunately, the wings of hawks, eagles, herons, flamingos, and cranes can span two wires at once, or brush an uninsulated transformer. The result is no mere shock. A raptor’s beak or feet can melt right off, or its feathers can ignite. Several captive-bred California condors have died exactly this way on being released, as have thousands of bald and golden eagles. Studies in Chihuahua, Mexico, show that new steel power poles act like giant ground wires, so that even smaller birds end up on the piles of dead hawks and turkey vultures below.

Other research suggests that more birds die by simply colliding with power lines than from being zapped by them. But even without webs of live wires, the most serious traps for migratory birds await in tropical America and Africa. So much land there has been cleared for agriculture, much of it for export, that each year there are fewer roosting trees to ease the journey, and fewer safe wetlands where waterfowl can pause.

Climate change is already suspected of breeding failures in seabirds such as northern guillemots, as their marine food supplies shift north of their rookeries off Scotland. As coastal salt marshes are inundated by rising seas, habitats of birds such as seaside sparrows and clapper rails may simply move inland with them, but suddenly drowned beaches and barrier islands could mean that shorebird species such as piping and Wilson’s plovers and least terns may be less lucky. Farther inland, habitats will depend on which plants thrive or don’t survive a changing habitat. As temperatures rise, some species will expand their range northward; already there are fewer orchard orioles in Texas, even as more appear in North Dakota. As happened at the end of the Pleistocene, however, if climate change further desiccates the American Southwest, species like the buff-collared nightjar might recede southward into Mexico. The impact is hard to quantify, but in North America and Europe, the numbers of some songbird species such as the cerulean warbler and the Bendire’s thrasher have fallen by two-thirds since 1975.

Without humans, some semblance of those wayside forests will return within a few decades. Two other major perpetrators of songbird loss—acid rain, and insecticide use on corn, cotton, and fruit trees—will end immediately when we’re gone. The resurgence of bald eagles in North America after DDT was banned bodes hopeful for creatures that cope with residual traces of our better life through chemistry. However, while DDT is toxic at a few parts per million, dioxins become dangerous at just 90 parts per trillion—and dioxins may remain until the end of life itself.

In separate studies, two U.S. federal agencies estimate that 60 million to 80 million birds also annually end up in radiator grilles or as smears on windshields of vehicles racing down highways that, just a century ago, were wagon trails. High-speed traffic would end when we do, of course. However, the worst of all manmade menaces to avian life is totally immobile.

Well before our architecture tumbles, its windows will mostly be gone, and one reason will be repeated pounding from inadvertent avian kamikazes. While Muhlenberg College ornithologist Daniel Klem was earning his doctorate, he enlisted residents of suburban New York and southern Illinois to record the numbers and kinds of birds crashing into that post–World War II home builder’s icon, the plate glass picture window.

“Windows are not recognized as obstacles by birds,” Klem tersely notes. Even when he stood them in the middle of fields, free of surrounding walls, birds failed to notice them until the final, violent second of their lives.

Big birds, little birds, old or young, male or female, day or night—it didn’t matter, Klem discovered over two decades. Nor did birds discriminate between clear glass and reflective panes. That was bad news, given the late-20th-century spread of mirrored high-rises beyond city centers, out to exurbs that migrating birds recall as open fields and forests. Even nature park visitor centers, he says, are often “literally covered with glass, and these buildings regularly kill birds that the public comes to see.”

Klem’s 1990 estimate was 100 million annual bird necks broken from flying into glass. He now believes that 10 times that many—a billion in the United States alone—is probably too conservative. There are about 20 billion total birds in North America. With another 15 million taken each year by hunting—that same pastime that snuffed mammoths and passenger pigeons—these numbers begin to add up. And there is still one more scourge that man has inflicted on birdlife, one that will outlive us—unless it runs out of birds to devour.

Ovenbird
Threat: Glass In summer they skulk on the forest floor, mostly away from such mysterious obstacles. But during spring and fall, when they venture on their long migrations, ovenbirds are among the millions of birds killed each year by flying against windows.

Wisconsin wildlife biologists Stanley Temple and John Coleman never needed to leave their home state to draw global conclusions from their field research during the early 1990s. Their subject was an open secret—a topic hushed because few will admit that about one-third of all households, nearly everywhere, harbor one or more serial killers. The villain is the purring mascot that lolled regally in Egyptian temples and does the same on our furniture, accepting our affection only when it pleases, exuding inscrutable calm whether awake or asleep (as it spends more than half its life), beguiling us to see to its care and feeding.

Once outside, however, Felis silvestris catus drops its subspecies surname and starts stalking as it reverts to being F. silvestris—wild cat—genetically identical to small native wildcats still found, though seldom seen, in Europe, Africa, and parts of Asia. Although cunningly adapted over a few thousand years to human comforts—cats that never venture outdoors generally live far longer—domestic cats, Temple and Coleman report, never lost their hunting instincts.

Possibly, they sharpened them. When European colonists first brought them, American birds had never before seen this sort of silent, tree-scaling, pouncing predator. America has bobcats and Canada lynx, but this fecund invasive feline species was a quarter-size version—a frightening, perfect fit for the enormous population of songbirds. Like humans, cats killed not only for sustenance but also, seemingly, for the sheer pleasure of it. “Even when fed regularly by people,” Temple and Coleman wrote, “a cat continues hunting.”

In the past half-century, as the world’s human population doubled, the number of cats grew much faster. In the American Veterinary Medical Association’s pet figures, Temple and Coleman found that from just 1970 to 1990, America’s cat count rose from 30 million to 60 million. The actual total, however, must also include feral cats that form urban colonies and rule barnyards and woodlands in far greater densities than comparable-sized predators like weasels, raccoons, skunks, and foxes, which have no access to protective human shelter. Various studies credit the average alley cat with up to 28 kills per year.

Farm cats, Temple and Coleman observed, get many more than that. Comparing their findings with all the available data, they estimated that in rural Wisconsin, about 2 million free-ranging cats kill a minimum of 7.8 million, but probably upwards of 219 million, birds per year. That’s in rural Wisconsin alone.

Nationwide, the number likely approaches the billions. Whatever the actual sum may be, cats will do very well in a world without the people who took them to all the continents and islands they didn’t already inhabit, where they now outnumber and outcompete other predators their own size. Long after we’re gone, songbirds must deal with the progeny of these opportunists that trained us to feed and harbor them.

California quail
Threat: Cats Many wild bird species could thrive in the altered habitats of suburbs and parks if they were not subjected to unnatural predation from free-roaming house cats. Birds that nest low or on the ground, such as California quail, are particularly vulnerable.

Ornithologist Steve Hilty, author of two of the world’s thickest field guides (to the birds of Colombia and Venezuela), has watched the decline of North American migratory songbirds tilt into a plunge as more Andean forests are cut each year for coffee or coca, forcing many species to funnel into ever-shrinking wintering grounds where there isn’t enough to feed them all. Without humans, could they return?

Fortunately, Hilty notes, “in South America, very few birds have actually gone extinct.” In a world without people to tend them, Colombia’s coca plants—native to the highlands of Peru and Bolivia but needing chemical help anywhere else—won’t last two seasons. Birds would reseed dope plantations with forest habitat; likewise, with no one to weed, native seedlings would soon battle coffee bushes for nutrients. In a few decades, shade from their canopies would slow Coffea arabica’s growth, and their roots would strangle that Ethiopian interloper until it choked.

Today Ecuador’s critically endangered pale-headed finch lives in only one Andean valley; Venezuela’s endangered grey-headed warbler is confined to a single mountaintop; and Brazil’s cherry-throated tanager is found on just a single ranch north of Rio de Janeiro. Without us and our agriculture, they’d be free to go forth, multiply, and migrate through renewed corridors. For these species and Homo sapiens to remain together on this planet, the question we must ask at this critical point in natural history becomes as much spiritual as ecological: “What would nature do?”

The answer, of course: restore equilibrium among predators and prey, and strike a proper blend of species in every ecosystem.

With or without us, in fact, that is just what nature will do. Whether both we and birds get to be part of that mix will depend partly on wise conservation, but largely it will come down to numbers. Via our little experiment, we’ve glimpsed how feathered creatures, jeopardized by our current pervasive presence, might revive and thrive in our absence. Somewhere between those extremes lies the equilibrium that we and nature seek. Either we stanch the relentless, million-every-four-days increase of humans to the planet—a challenge but far easier than replacing a passenger pigeon—or nature, as she has always done when a species exceeds its habitat’s carrying capacity, will do so for us.

May it never come to that, lest too many lovely birds go down with us.

Besides The World Without Us, Alan Weisman has written for National Public Radio, Harper’s, and The New York Times Magazine. He teaches international journalism at the University of Arizona, in Tucson.

What You Can Do

For information about protecting birds from collisions with windows in your home, click here. The U.S. Fish and Wildlife Service is working with the utility industry to prevent electrocution on power lines and collisions with towers. “Avian Protection Plan Guidelines,” a document written in collaboration with the Edison Electric Institute, recommends, among other things, that utilities place covers on transformers, wires, and jumper wires, and build perches for ospreys and other raptors on poles away from live power lines. The guidelines are voluntary, so urge your utility provider to adopt these measures, and to join the Avian Power Line Interaction Committee. To learn more about what utilities say they are doing to protect birds, click here.Back to Top